SIM Preference rules for single-modem PepWaves

I now have my dual SIM (single modem) PepWave Max BR1 Mini operating with two SIMs:

  • Verizon 1GB/$15
  • ATT 15GB/$35
    I’ll mostly be using this in California back roads, where Verizon is usually but not always the best signal. Since I have more GB on ATT, I’d like a setup where the device will default to ATT, but will not get stuck on ATT if the Verizon signal is much better. Since this BR1 Mini only has a single modem, and per How to prioritize Cellular #1 connection over #2 - #9 by MartinLangmaid the search process for switching SIMs can take 3+ minutes, I also want to make sure the connection is not constantly dropping.

Here’s what I’m thinking for settings:

  • SIM: both
  • Preferred: SIM B (ATT)
  • Fallback to Preferred SIM when: Device is idle (30 minutes) or Non-Preferred SIM is connected for 240 minutes

In my understanding, this means “It’s OK to use the Verizon SIM, but if nobody is using the internet for 30 minutes, OR we’ve been using Verizon for 4 hours, then try again to go back to ATT”.

Questions:

  • What does “Device is Idle” mean? No WiFi connections? WiFi connections, but no data? How is this “idle” defined?
  • I see there is also a “Signal Threshhold” setting:

How does this work with dual SIMs? If you set a threshold, and both SIMs are below it, will the PepWave be offline? Or will it prefer whichever SIM has better signal?

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Not sure how well device idle works. Because even a cell phone with no apps open and the screen off will still be “active”. I think you need to completely disconnect all client connectivity for it to be truly idle.

Signal threshold is another form of “health check”. I keep mine set to 1 bar.

The measurement is ONLY for the currently ACTIVE SIM. It does not have any way to continuously measure both. Failover between ATT & VZW will take 1-2min for the modem to reset. If the secondary carrier also wont connect I would think after X-number of retries it would flip back to primary.

Also remember that signal strength is no guarantee of “usable bandwidth/performance”

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I tested this in the field this week, and have some more info.

Although I had set the device to prefer SIM B, at one point I realized it was on SIM A. Checking the logs, it was clear that SIM B had failed the Health check at one point, which triggered a switch.

So the logic of which SIM is used is quite complicated as a number of settings can cause a switch:

  • preferred SIM
  • Fallback “Device is idle for ____ minutes”
  • Fallback “Non preferred SIM is connected for _____ minutes”
  • health check
  • Signal threshhold settings

It would be nice if PepLink could give us more info.

Specific questions:

  • How is “Idle” defined? Is it lack of WiFi client connections? Or lack of packets being sent from Client connections?
  • Does the “Signal threshold” setting override other settings? For example, if I have “Prefer SIM B” and “require 2 bars of signal” - what happens if SIM A has 2 bars and SIM B has 1 bar. Which SIM would be used?
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